This invention relates in a first aspect to a gas sampler for a portable gas analyser, and in a second aspect to an analyser provided with such a sampler.
Portable gas analysers are known for use in the measurement of the concentration of gas in stacks and ducts of industrial processes for the purpose of emissions monitoring, and combustion control. In practice, the analyser extracts a small amount of gas from the flue usually via metal tube or probe mounted in the stack or duct and a length of hose. In order to assure accuracy of measurement, it is necessary to remove the water content from the gas, usually by means of a cooler. Traditionally such coolers require electrical power (usually mains), are bulky and not very practical to use with a portable analysers which are usually battery powered.
A basic object of the invention is the provision of an improved gas sampler and portable gas analyser.
According to a first aspect of the invention, there is provided a gas sampler for a portable gas analyser, wherein the sampler comprises an integral cooler or chiller operable by means other than electrical power, through which cooler or chiller the gas sample is passed prior to being conveyed to a gas analyser.
According to a second aspect of the invention, there is provided a battery powered, portable gas analyser in combination with a sampler in accordance with the first aspect.
The integration of a non-electrically powered cooler or chiller into the sampler firstly ensures that the required removal of water vapour from the gas sample may be satisfactorily achieved before the sample is introduced into the analyser, thereby avoiding inaccurate analysis due to the presence of water vapour, and secondly ensures that there is neither a drain on the battery capacity nor a requirement for increased battery capacity for activation of the cooler or chiller, whilst the rate and volume of gas flow through the cooler or chiller can be readily adjusted on site, by known control techniques, to ensure that for whatever gas temperature is involvedxe2x80x94which will of course vary from site to sitexe2x80x94there is sufficient dwell time of the gas sample within the cooler or chiller, for the dew point to be attained to condense the water vapour, so that the gas sample is then left xe2x80x9cdryxe2x80x9d, allowing the analyser to make a true xe2x80x9cdryxe2x80x9d measurement.
The sampler is provided with an industry-standard probe.
The sampler is provided with a connection eg for a flexible hose, for gas sample transfer to a gas analyser.
The cooler comprises a vessel adopted to contain a cooling agent to remove heat from the gas sample.
The cooler comprises a cooling agent reservoir.
The cooling agent is a measure of crystals to which water is then added to initiate an endothermic chemical reaction.
The crystals are of ammonium nitrate, or potassium bromide.
The crystals and water are supplied as a package, with the water in a rupturable bag.
The vessel also houses an expansion chamber for the gas sample, the chamber having an inlet, and an outlet for the gas sample, and the chamber being subjected to the cooling effect of the endothermic reaction, whereby sufficient heat is removed from the gas sample flowing through the chamber to attain the dew point.
A catch pot is associated with the expansion chamber to collect water that is condensed out of the gas sample by lowering of the temperature of the gas sample through its dew point.
The sampler is interchangeable to provide a variety of lengths.
The sampler contains an integral flue gas temperature thermocouple and a replaceable particulate filter.
The chiller contains an impinger, a water catch pot and a cooling medium reservoir.